The merits of breast-feeding are well documented in the scientific literature. A number of advantages have been noted which include nutritional, immunological, psychological and other general health advantages. A list of the merits of human breast milk as compared to artificial feed or formula would include ideal nutritional content, better absorption, fewer food related allergies, more favorable psychological development, better immunological defenses, and a substantial economic advantage. Another benefit to exclusive breast-feeding includes positive effects on development of an infant's oral cavity resulting in proper alignment of teeth and other related benefits.
For various reasons, however, exclusive breast-feeding is not always possible. An example of this would be where a nursing mother cannot produce enough breast milk to feed her infant. In such cases, an artificial feed may be used to supplement breast-feeding. A nursing mother returning to work may employ a breast pump to express milk to be given to her infant at a later time. In the event that an infant is fed with an artificial formula or previously expressed breast milk, it is conventional that a bottle provided with an artificial nipple is used to feed the infant.
The mechanical aspects of breast-feeding are significantly different compared to that of bottle-feeding. In breast-fed babies, the tongue action appears to be of rolling or peristaltic motion. However, the tongue action for bottle-fed babies is often considered to be more piston-like or a squeezing motion. In order to stop the abundant flow of milk from a bottle with an artificial nipple having a large hole in the end, infants might be forced to hold the tongue up against the hole of the nipple to prevent the formula from gushing forth. This abnormal activity of the tongue is referred to as tongue thrust or deviate swallow. When breast-fed babies are not sucking or swallowing, they may rest with the nipple moderately indented by the tongue, while bottle-fed babies rest with the teat expanded, i.e., indenting the tongue. The differences between the tongue movements and rest position of the tongue and breast-fed and bottle-fed babies are probably due to the properties of the artificial nipple.
In the past, artificial nipples were generally made of latex and had only one single aperture. The aperture could be enlarged or new apertures could be opened to increase the flow of fluid by using a device to distend the aperture or pierce the latex, such as a hot needle. Enlarging the existing aperture or adding new apertures is done to increase the flow rate necessary or desirable for the infant. The amount of milk a baby requires during feeding may vary by size (growth) of the baby, appetite or nourishment.
Silicone nipples have become increasingly popular. Silicone nipples have a propensity to easily tear. Therefore, enlarging the existing aperture, or opening additional apertures is not very feasible. Consequently, silicone nipples are offered in a variety of flow rates with additional or larger apertures.
The undesirable effects of existing artificial nipples include a relatively constant maximum flow rate as the baby applies suction pressure, or negative pressure, to the artificial nipple. The artificial nipple has to be replaced when an increase or decrease in flow rate is desired.
It would be desirable to have an artificial nipple that provides a variable flow rate responsive to changes in suckling, such as in negative pressure from the baby, in addition to reducing or eliminating the need for different artificial nipples for different flow rates. The present invention is believed to satisfy this desire, among other things.